Rachel and Leah were sisters in the bible. Jacob fell in love with Rachel and intended to marry her. But a heavily-veiled Leah was substituted for Rachel at the wedding, as it was expected that the older sister marry first. Jacob later married Rachel as well.
Leah bore Jacob six sons and one daughter, but Rachel could not conceive. Instead, she offered Jacob her maidservant, Bilhah, as a surrogate. Bilhah gave birth to two sons. Leah then did the same thing, offering Jacob her maidservant Zilpah who bore two sons.
Rachel eventually gave birth to her own sons: Joseph and Benjamin.